package section_10;

import java.util.Arrays;
import java.util.Scanner;

/**
 * @Author ZhangGJ
 * @Date 2019/10/13
 */
public class LotteryDrawing {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        System.out.print("How many numbers do you need to draw? ");
        int k = in.nextInt();

        System.out.print("What is the highest number you can draw? ");
        int n = in.nextInt();

        // fill an array with numbers 1 2 3 . . . n
        int[] numbers = new int[n];
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = i + 1;
        }
        // draw k numbers and put them into a second array
        int[] result = new int[k];
        for (int i = 0; i < result.length; i++) {
            // make a random index between 0 and n - 1
            int r = (int) (Math.random() * n);

            // pick the element at the random location
            result[i] = numbers[r];

            // move the last element into the random location
            /*
            每次把选中的数字用数组最后一个替换，然后n-1，数组长度没变，但是n变为n-1了，数组最后一个元素不会再被遍历到
             */
            numbers[r] = numbers[n - 1];
            n--;
        }

        // print the sorted array
        Arrays.sort(result);
        System.out.println("Bet the following combination. It'll make you rich!");
        for (int r : result) {
            System.out.println(r);
        }
    }
}
